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SecretSnow
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What does it really mean in physical term? Does it mean no friction? No loss of mechanical energy? Thanks!
Slipping means that surfaces slide with respect to each other--there is relative motion between the surfaces. There may or may not be friction.SecretSnow said:What does it really mean in physical term? Does it mean no friction? No loss of mechanical energy? Thanks!
You do still have rolling friction which, I believe, is static friction occurring at the point of contact?Doc Al said:Slipping means that surfaces slide with respect to each other--there is relative motion between the surfaces. There may or may not be friction.
If there is no slipping, then the surfaces do not slide at the point of contact. There may or may not be friction involved. An example would be a ball rolling without slipping. At any instant, the point of contact of the ball is not moving with respect to the surface. There is no energy loss due to friction, since there is no motion of the contact point (at least instantaneously).
Rolling friction is a different kind of thing than ordinary static friction. (At least as I understand it.) But you're right, you could have both static friction and rolling friction even though you are rolling without slipping. (Often rolling friction is ignored.)Hurkyl said:You do still have rolling friction which, I believe, is static friction occurring at the point of contact?
lewando said:It means there is plenty of friction. There is no mechanical energy loss. Slipping implies no friction (also no energy loss). Sliding implies friction exists and has been overcome and with a resulting energy loss. Ultimately, how the word is used in the context of the question is to be considered.
Friction actually helps the ball go higher up the hill. It helps convert rotational KE into translational KE. Since there's no slipping, no work is done by the friction and thus no mechanical energy is 'lost'.SecretSnow said:Also, if this is the case, why is it that a ball rolling uphill without slipping has friction directed uphill?
OK.SecretSnow said:I'm guessing that because v=rw is towards downhill, friction is uphill.
What do you mean by that?Meaning that this friction belongs to the rotating one.
Does what apply?However does this apply to only rotating object?
No. When rolling downhill, the ball is speeding up and thus the friction must provide torque to give a rotational acceleration.Also does it mean that direction of friction of the ball rolling downhill without slipping is pointing downwards too?
The book is correct. Realize that a ball rolling downhill without slipping has a smaller acceleration than if there were no friction. Some of the energy is going into rotational KE.I noticed that the question in the textbook I use has friction pointed upwards though.
In order to roll uphill without slipping, at any point the velocity must meet the criteria of v = ωr. As the ball slows down, friction must act to decrease the rotational speed accordingly.SecretSnow said:I see. If the friction must provide torque to give the ball a angular acceleration, meaning if it goes downhill the friction is uphill to make it roll, then why does the ball going uphill still have a friction still uphill to make it stop rolling? Although I know that if without friction, the ball will still stop rolling due to gravity What is the rationale of having the friction upwards?
Consider the direction that the ball rolls when it goes uphill on a frictional surface (say the ball is going from left to right up the hill--therefore it would appear to be rolling in a clockwise manner). At the point of contact between the ball and surface, what direction would you apply a force to make the ball stop rolling?SecretSnow said:I see. If the friction must provide torque to give the ball a angular acceleration, meaning if it goes downhill the friction is uphill to make it roll, then why does the ball going uphill still have a friction still uphill to make it stop rolling?
Actually, without friction the ball will not stop rolling (assuming that it was somehow rolling in the first place--if no friction, the ball will not begin to roll upon contact with the surface).Although I know that if without friction, the ball will still stop rolling due to gravity What is the rationale of having the friction upwards?
lewando said:Consider the direction that the ball rolls when it goes uphill on a frictional surface (say the ball is going from left to right up the hill--therefore it would appear to be rolling in a clockwise manner). At the point of contact between the ball and surface, what direction would you apply a force to make the ball stop rolling?
Actually, without friction the ball will not stop rolling (assuming that it was somehow rolling in the first place--if no friction, the ball will not begin to roll upon contact with the surface).
No. There's only one force of friction acting on the ball rolling uphill without slipping. And it acts up the hill. That same force affects both the rotational and translational motion of the ball.SecretSnow said:By the way, when I said that friction belonging to the rotational part, I was trying to ask if there's another friction opposing the uphill motion as a whole.
Why won't what roll? To sum up--no friction, no (surface-induced) rolling (or stoppage of rolling--in the event that as the ball was sent up the frictionless hill, you made it spin as a result of frictional contact from your hand). Just a lot of slipping.SecretSnow said:Why won't it roll?
That's right. When the spinning ball reaches the highest point it can on a frictionless hill, the ball will continue to spin at a constant angular velocity (say clockwise). As the ball descends back down it will continue to spin at the same constant angular velocity (still clockwise).If there's a friction uphill to make it stop rolling, then without the frictoon wouldn't it continue rolling?
lewando said:Why won't what roll? To sum up--no friction, no (surface-induced) rolling (or stoppage of rolling--in the event that as the ball was sent up the frictionless hill, you made it spin as a result of frictional contact from your hand). Just a lot of slipping.That's right. When the spinning ball reaches the highest point it can on a frictionless hill, the ball will continue to spin at a constant angular velocity (say clockwise). As the ball descends back down it will continue to spin at the same constant angular velocity (still clockwise).
"No slipping" refers to a situation in which an object is moving without any sliding or rolling motion. This means that there is no relative motion between the object and the surface it is in contact with.
"No slipping" and "slipping" refer to two different types of motion. "No slipping" means that there is no relative motion between an object and the surface it is in contact with, while "slipping" refers to a situation in which there is sliding or rolling motion between the object and the surface.
Examples of "no slipping" include a car driving on a flat road, a person walking on a level surface, and a ball rolling on a level ground without any additional force applied.
The concept of "no slipping" is important in physics because it is a fundamental principle in the study of motion and forces. It helps us understand the relationship between an object and the surface it is in contact with, and how external forces can affect the motion of an object.
Friction is the force that opposes motion between two surfaces in contact. In the case of "no slipping", there is no motion between the object and the surface, therefore there is no friction present. However, in situations where there is slipping or sliding motion, friction plays a crucial role in determining the motion of the object.